A recent mobile communication system is evolving into a high-speed and high-quality wireless packet data communication system for providing a data service and a multimedia service, outgrowing an initial voice-oriented service. In order to support such a high-speed and high-quality wireless packet data transfer service, various mobile communication standards such as high speed downlink packet access (HSDPA), high speed uplink packet access (HSUPA), long term evolution (LTE), and LTE advanced (LTE-A) of 3rd generation partnership project (3GPP), high rate packet data (HRPD) of 3GPP2, and 802.16 of Institute of Electrical and Electronics Engineers (IEEE) have been developed. In particular, LTE/LTE-A/LTE-A Pro (hereinafter LTE) continues to develop and evolve standards to improve system capacity and frequency efficiency.
Typically, the LTE system can greatly increase a data transfer rate and system capacity by using carrier aggregation (CA) technology capable of operating the system using a plurality of frequency bands. In addition, the frequency band currently used in the LTE system is generally a licensed band (licensed spectrum or licensed carrier) used by an operator having authority.
However, since a typical frequency band (e.g., a frequency band of 5 GHz or less) that provides a mobile communication service has been already occupied by another operator or another communication system, an operator may often fail to obtain a number of licensed band frequencies and thus have difficulty in expanding the system capacity by using the CA technology.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.